Field of the Invention
The present invention relates to an imprint apparatus, and a method of manufacturing an article.
Description of the Related Art
As micropatterning of semiconductor devices is requested more and more, a microfabrication technique of molding an uncured resin on a substrate using a mold and forming the pattern of the resin on the substrate has received attention. The technique is referred to as an imprint technique, and can form a fine structure on the order of nanometer on the substrate. For example, in an imprint apparatus adopting a photo-curing method as a curing method of a resin, an ultraviolet-curing resin (imprint material) is applied to a shot region (imprint region) on the substrate, and the resin (uncured resin) is molded using a mold. Then, the mold is separated (released) after curing the resin by irradiation with ultraviolet rays, thereby forming the pattern of the resin on the substrate.
In general, an atmosphere within an imprint apparatus is air. Therefore, if the mold and the resin are pressed against each other, the air stays between them, and then turns into a residual gas which may form bubbles in the resin. In this case, a trouble may occur in a pattern to be transferred onto the substrate. This makes it impossible to form an accurate pattern on the substrate. To cope with this, it is considered to wait until the residual gas is dissolved, diffused, or penetrates into the resin and the mold to disappear. However, this takes much time to perform an imprint process.
To solve this, U.S. Pat. No. 7,090,716 proposes an imprint apparatus which uses a penetrating gas as an imprint atmosphere, and dissolves or diffuses the penetrating gas remained in a resin and a mold, thereby quickly reducing the residual gas. Also, Japanese Patent No. 3700001 proposes an imprint apparatus which uses, as an imprint atmosphere, a condensable gas which condenses along with a pressure rise (increase) when a mold and a resin are pressed against each other. The condensable gas is liquefied when remaining, and its volume is reduced to a few hundredth as compared to that in the gaseous form. This makes it possible to suppress an influence on the pattern formation of the residual gas. When using the condensable gas, since the viscosity of the resin is reduced by absorbing the liquefied condensable gas into the resin, the spreading speed of the resin on the substrate is increased, thus achieving the pattern formation in a shorter time.
On the other hand, if the penetrating gas and the condensable gas enter the optical path of, for example, an interferometer which measures a substrate stage position, the interferometer cannot measure the substrate stage position accurately. To cope with this, Japanese Patent Laid-Open No. 2012-164785 proposes a technique of using, as an imprint atmosphere, a gas mixture which is obtained by mixing a penetrating gas and a condensable gas, and adjusting a mixture ratio between the penetrating gas and the condensable gas to reduce a measurement error by the interferometer (to obtain the same refractive index as that of air).
In pattern formation by an imprint process in a condensable gas atmosphere, however, the liquefied condensable gas absorbed into a resin is discharged outside after releasing, thus possibly deteriorating the shape of the pattern which has been formed on a substrate. There are tendencies of, for example, an increase in the surface roughness of the pattern, a reduction in the density of the resin, the narrowness of the line width of the pattern, and a deterioration in the sectional shape of the pattern. These tendencies are stronger as the concentration of the condensable gas increases. On the other hand, a time for the pattern formation can be reduced as the concentration of the condensable gas increases. Thus, a trade-off relation exists between accurate pattern formation and an increase in a throughput (productivity).